Electric welding and reactor



S. R. BERGMAN.

ELECTRIC WELDING AND REACTOR.

APPLICATION FILED .IUNIEZES 1920.

PatentedSeptZLlfJZO.

m t -t e t ma A R s .m m Q Current QUNITED'STATES PAFITENT OFFICE- SVENB.- .IBEBGMAN,

OF NAHANT, MASSACHUSETTS, ASSIGNOR TO GENERAL ELECTRIC COMPANY, ACORPORATION OFINEW YORK.

ntncr'mc WELDING AND rmac'ron.

Application'flled June 25,

To all whom it may concern: y

Be it known that I, SVEN R. BERGMAN, a subject of the King of Sweden,residing at Nahant, county of Essex, State of Massa- 5 chusetts haveinvented certain new and useful improvements in Electric Welding andReactors, of which the following is a specification.

' My invention relates to electric arc welding, cutting or repairing andto a new type of reactor that is particularly adapted for circuits ofthe type used in electric welding, cutting or repairing, in whichcircuits the current must be adjusted overa considerable range in orderto meet the conditions imposed by various classes of work.

An object of my invention is to provide an apparatus for circuits of thetype referred to which shall insure a proper reactance voltage forefiicient operation eventhough the current be adjusted over a widerange.

A further object of my invention is to provide an apparatus for electricarc welding, cutting or repairing which shall adjust the-reactance tothe proper value for efiicient operation with any given current withoutthe necessity for care or skill on the part of the operator.

A further object of my invention is to provide a new type of reactor inwhich the inductance shall be automatically and inherently adjusted to"difierent values. for diflerent values of current therethro'ugh. 35Electric arc welding, cutting or repairing with direct current requiresthe presence of acertain amount of reactance in the circuit to steadythe are. This reactance is commonly provided by connecting a reactor mgcircuit. As is well-known to. those skilled in the electrical art suchreactor has no efi ect on the current in the circuit while the currentis steady, but becomes immediateiy effective to develop anelectromotive-force whenever a change in the current produces a changeof the flux threading the turns of the reactor. Such electromotiveforceis always in a direction to oppose the tendency of the current to changeand therefore by the use of a proper amount of reactance the currentthrough the circuit is maintained reasonably constant even orself-inductance coil in series in the weld- 3 Specification of LettersPatent. Patented Sept. .21, 1920.

1920. Serial No. 391,721.

to ununiformities in the work or electrode,

but in metallic arc welding are mainly due to variations in the lengthof the arc, caused by a failure to feed the electrode toward the work atthe exact rate it is being consumed by the welding current. In order tomake it unnecessary to provide a separateapparatus for each currentvalue required in such are circuits, it is customary to ing the currentdelivered to the welding circuit, and one such apparatus which I havedesigned for metallic arc welding is arranged with a number of terminalsgiving respective] 75, 100, 125, 150, 175 and 200 amperes. here carbonarcs are used much provide means for adjust greater values of currentwill be encountered.

have discovered that a reactor which is satisfactory for "amperes isalmost useless for the higher values of currents, owing to the fact thatit is impossible to design a practical reactor having a fixed number ofturns and a fixed air gap reluctance, which type of reactor in which theadjustment of" the reactance shall occur automatically and inherently.

My invention will be better understood from the following descriptiontaken in connection with the accompanying, drawings, and its scope willbe pointed out in the appended claims;

Referring to the accompanying drawings Figures 1 and 2 are circuitdiagrams showing embodiments of my invention; Fig. 3 is an explanatorydiagram; Figs. 4:, 5 and 6 are detail views showing various forms of myreactor construction; Fig. 7 shows a variation of the form shown in Fig.4 and illustrates one way of holding the parts assembled; Fig. 8 is asection of Fig. 7 on the line 7-7 and Fig. 9 represents.an'alternativeair gap construction. I

Referring to Fig l, a pair of direct cur drawing wherein the slidingcontact machine,

arranged to be saturated and the other pairrent mains 1, 2 arerepresented as connected through a'series resistor 3 and a seriesreactor 4 to supply current to an electric welding, cutting or repairingcircuit comprising the electrodes 5 and 6. In order to control thecurrent, the resistor is made adjustable and such adjustability isindicated in the 7 is arranged to 'move along the resistor 3. In orderto provide the amount of reactance voltage requisite for properoperation with each value of current, I have arranged means to adjustthe inductance of the reactor 4 simultaneously with the adjustment ofthe resistor 3. In the arrangement shown in Fig. 1, this is accomplishedby arranging a sliding contact 8 to cooperate with contacts 9 which areconnected to taps leading from the winding of reactor 4. The slidingcontact devices 7 and 8 are represented as mounted upon a common member9' so as to move together.

The arrangement is such that the number of turns in the reactor isincreased when the resistor is adjusted to reduce the current and viceversa. In this way the inductance of the reactor is changed whenever thecurrent is changed and the proper amount of reactance voltage is insuredfor each value of the. current;

It is also possible to adjust the inductance of the reactor by changingthe air gap in such a manner as to make the gap smaller for the smallercurrents. An actual physical adjustment of the air gap, however, is notfeasible in practice because of the high magnetic pulls encountered. Inorder to avoid the difliculties incident to a movable core reactor andto avoid the complication introduced by a switching arrangement foradjusting the turns of the reactor, I have produced a reactor. in whichtheinductance is inherently and automatically adjusted in accordancewith changes in the current through the reactor. By reason of thisinherent action I am enabled to do away with all moving devices eitherinternal or external to the reactor for controlling justment.

Fig. 2 diagrammatically represents my improvedtype of reactor in serieswith a direct currentgenerator of the ty e shown inmy Patent No.1,340,004, grante May 11, 1920. This generator .is a constant speed onepair of poles 10 of which are of poles 11 of which are unsaturatedduring the normal-operation. The armature is provided with a pair ofmain brushes 12 and 13 and an auxiliary brush 14. The arrangement issuch that the voltage between brushes 12 and 14 is produced by saturated'poles 10 only, while the voltage between brushes 12 and 13 which areconnected to the welding circuit is produced by the flux 1n both thesaturated and unsaturated poles.

i-ts'ad- .slfijs apparent that the voltage between brushes 12 and 14 isconstant and the exciting windings 15 and 16 are suppliedfrom thisconstant voltage. The direction of windings 15 and 16 is such thatfthemagnetomotive forces of these windings tend to produce fluxes and E. M.Fds in the same direction between brushes 12 and 13. An adjustableseries differential winding 17 carrying the'current in the weldingcircuit is arranged upon the poles'llf- The armature reaction of thegenerator is arranged so that the component thereof in line with poles11 assists the windings 17 and so that the component thereof in linewith poles 10 assists the windings 15. It is apparent that variations inthe welding current have little effect upon the flux in the line ofpoles 10, as thus arranged, since these poles are saturated duringnormal operation and it is apparent that variations in the weldingcurrent 'havea very marked effect] upon the flux in the line of poles11, since,these--poles are always under-saturated. The windings are soarranged that with no current flowing, the voltage between the brushes12 and 13 will. be that necessary to strike the arc,

and so that with a certain valueof load cur-- rent, preferablyv abouthalf load, the resultant flux in the poles 11 will be zero. At such aload the voltage between the brushes 12 and 13 will be equal to thevoltage between the brushes 12 and 14. When-the welding currentincreases above this value, the flux in poles 11 builds up in the oppo-"site direction so that the electromotive-force between brushes 13 and14 increases, but.

polarity to that between 14.. Therefore, the voltage equal to thebrushes 12 and 14 less the' stantially equal to the voltage between,

brushes 12 and 14 and opposed thereto. It is apparent therefore that thevoltage between the welding circuit brushes 12 and 13 a is the algebraicsum of the voltage between.

brushes 12 and 14 and brushes'13and14,

while the voltage between brushes 12 and 14 is at all times constant. Inorder to adjust the welding current to different values,

taps are provided by which the number of turns in theseries-diii'erential winding 17 may be varied.

The reactor 4' of Fig. 2 is connected in series in the. welding circuitwhich leads through any well-known form of circuit controlling device 18to the electrodes 5 and 6. The reactor is represented as provided with ashell type core 19 having an air gap 20 in the middle leg. The coi1'21of the reactor .is represented as wound upon this middle leg of thecore. I propose to construct one the air gap, I propose to reduce thecrosssection of the core adjacent the air gap in such a way thataprogressive saturation will be produced as the current through thereactor increases, the arrangement being such that the flux distributionis shifted in a manner to increase the effective air gap reluctance.Accordingto one form of my invention, I arrange slots 22 in the iron insuch manner that where the air gap is smallest the slot is longest. Thisprovides for a variable reluctance in serieswith the air gap. Thus, asthe ampere turns of the .coil change the saturation will take place fromleft to right in Fig. 4. The saturation, in other words, will shift thepoint of mimmum gap toward the point of maximum ga In order to explainthe principle of my invention, consider =first the efiect of an actualchange in the mechanical dimensions of an air gap. In Fig. 3 'thestraight lines marked i and 1" show the variations of flux which takeplace with variations of current with air gaps of the several dimensionsindicated. The curve 23 of Fig. 3 represents the saturation curve of myimproved reactor. At zero current'this curve is tangent to the curvemarked, Hence, at that point the rate of change of flux due to thechange in current is equlvalent to that due to a gap. At the point wherecurve 23 cuts the J; ga curve, the tangent will be parallel to the 1'gap curve. Hence, at that point the rate of change of the flux due tocurve 23 at. anypoint will give the rate of variable the change in thecurrent is equivalent -.to that due to a1" gap. Since the tangent tochange of the flux due to a change in eurrent, it is obvious that thisreactor is equlvalent in'its operation to a reactor havin a gap whichvaries from if to 1' in len h;

n the modification shown in Flg. 4, the p 4 length of the slots 22 isvaried in such a upper edges of the slots is not parallel to manner thata line drawn tangent to the v the upper face of the pole .piece 24, but

makes an angle therewith about equal to the angle between the polepieces 24; and 25. This arrangement somewhat Increases the maximumeflective air gap over that roduced in the arrangement lndicated in, ig.1 and shown more clearly in Fig. 7. 1

Fig. 5 shows. one method of-building up a laminated core structurehaving the middle leg constructed to provide an inherently adjusted airgap. In Fig. 5 both polepieces 24 and 25 are slotted, and but two shapesof laminations 26 and 27 are required to build up the reactor.

seam to be welded. In a Fig. 6 shows a modified arran ement-in which buta single shape of punc requ red to build up t e reactor. gap in Fig. 6is re resented as tapering both waIys from the mi dl in 28 is 'I he air1 order to avoid waste in material and in order to enable less expensivedies to be used, I preferably construct the middle leg of the reactor asshown in Figs. 7 and 8. One simple die only need be used and the returnpath of the core may be made up of straight pieces sheared to the properlengths and built up in any manner well-known in the art. The oneapparent disadvantage of such a construction lies in the large number oflap joints which are used, and, which for a transformer would not beadvantageous; but in the case of a reactor containing an air -gap in themagnetic circuit the additional reluctance of the lap joints isnegligible. I prefer to rivet the parts of the center leg together bythe aid of heavy end sheets 29 and 30 made .of brass and rivets 31insulated by the aid of 32 and mica washers 33.

Instead of using a simple air gap the equivalent of the air gap may besecured by ticularly in connection with are weldingcircuits, it will beobvious to those skilled in the art that in its broadest aspects myinvention is not limited to such circuits, but is applicable to anycircuit in which a reactor is necessary to smooth out fluctuations inpaper bushings art of slotting the iron as shown in Fig. 9. The

current and in which the current must be adjusted through a considerablerange of values. An example of such a circuit may be taken from the artof line welding machines, inwhich a roller electrode moves over thearatus of this type a series reactor is use to provide the voltagenecessary to break down the high resistance due to scale or other.irregularities which are encountered and to weld sheets ofdiiferentthickness different values of current are required.

What I claim as new and desire to secure by Letters Patent of the UnitedStates, is

1. A system comprising a source of direct current, a load clrcuitsupplied thereby adapted to provide wide and sudden changes inresistance, means for adjusting the current supplied from said source tosaid lead I circuit and a reactor in series in said lead varycharacterized by the fact that ad-- justments of said current arearrange the inductance of said reactor.v

2. .An arc welding system comprising. a source of direct currentconnected to supply current to a welding circuit, means whereby thewelding current supplied at any given voltage may be adjusted and areactor in series in said welding circuit. characterized by the factthat adjustments of thewvelding current are arranged to vary theinductance of said reactor.

3. An arc welding system comprising a welding circuit, a source ofdirect current for supplying welding current to said circuit, meanswhereby the welding current supplied at any given voltage may beadjusted and a reactor in series. in the welding circuit constructed andarranged inherently to adjust the efi'ective air gap of said reactor inaccordance with adjustments in the weld-- ing current. Y

4. A reactor comprising a coil, and a magnetic core provided with an airgap characterized by the fact that said core is provided with portionsadapted to become progressively saturated so as inherently to vary thereluctance of saidair gap with changes in K current in said core. v

5. A reactor comprising a coil and a flux path provided with a portionvarying from a minimum to a maximum length and constructed and arrangedto have a reluctance substantially independent of variations in currentthrough said coil, and a portion in series with said first portionarranged to .vary the reluctanceand change the flux disof magneticmaterlal provided with a tapered portion to produce an air gap varyingfrom aiminimum to a maximum length, said tapered portion being reducedin cross sec: tion' whereby saturation causes the effective air gap toincrease with increasing current through said coil.

7. reactor comprising a coil and a core of magnetic material providedwith an air gap, said core being constructed and arranged to becomesaturated adjacent said gap so as inherently to increase the effectivelength of said gap as the current through said coil increases.

8. A reactor comprising a coil and a core of magnetic material providedwith a fixed air gap of gradually varying length, said core beingslotted adjacent a face of said air gap the depth of sald slots beinggreatest near the shortest part of said gap and gradually decreasingtoward the longest part of said gap, whereby the reduction in crosssection caused by said slots causes the saturation dueto increasedcurrents in said coil to vary the effective len h of the 'gap.

In witness whereof, have hereunto set my hand this 23rd da of June 1920.

' SV N R. BERGMAN.

